Socialite/reality show star Tinsley Mortimer has another new man in her life.

The platinum blonde has been dating 26-year-old nightlife player Brian Mazza, who first met her while she was shooting a scene for her CW show, “High Society.”

Mortimer and Mazza — vice president of hospitality at the Paige Group, which owns Manhattan restaurants The Hill and Ainsworth, as well as Dune in Southampton — were spotted dining at Ainsworth on Tuesday, and later popped by the Ace Hotel. “They looked very couple-y,” says a spy. “They kissed a lot and left hand-in-hand.”

Mazza made an appearance in the first episode of “High Society,” though most of the screen time devoted to Tinsley’s love life has centered on her relationship with Prince Casimir Sayn-Wittgenstein-Sayn.

Adds our source, “Tinsley was linked in the press to both the prince and to [former ‘American Idol’ contestant] Constantine Maroulis, but she has been talking to Mazza for a while. They’ve been hanging out together a lot of late.”

Mazza tells us, “What started out as a reality show stunt has turned into a real relationship. We’re having a good time going out to clubs and to dinners. But I don’t want to get into anything personal.” He said Mortimer wasn’t seeing anyone else at the moment.

Meanwhile, Mortimer’s relations are hellish with her show rival Devorah Rose, editrix of the Hamptons magazine Social Life. Sources say Rose is fuming over the way the show is edited to make her look like a witch.

One friend said, “Devorah is convinced there is a conspiracy between the producers and Tinsley . . . She feels manipulated, she is scared and is getting hate mail. And she knows it’s only going to get worse.”

Meanwhile, Tinsley had a cozy lunch at Nello the other day with her estranged husband Topper. “They were there so long, it almost became dinner,” said one witness.